So, what do you do when hunger inevitably strikes? Here's a quick guide on when to cave and when to carry on fasting.

Should you feel hungry when intermittent fasting?

First, should you even feel hungry when you fast? This is actually one of the most common questions I get about intermittent fasting. And the answer is yes, hunger is completely normal. When you first start incorporating intermittent fasting into your routine, you will likely feel hungry after a few hours simply because your body is used to having constant access to food.

But don't worry, feeling hungry does not mean you are doing anything wrong or that you failed at fasting. It is actually due to decreases in glucose levels. The dip in glucose results in hunger pangs, BUT once your body gets used to intermittent fasting, glucose fluctuations will not affect you as much. Translation: You won't feel hungry every time you fast. Once you get in a good rhythm with fasting, that I-have-to-eat-right-now feeling will likely subside.

Most of us living on the Western diet—even a healthy Western diet—are used to glucose spikes and falls. The falls are what usually prompt us to eat. When you start intermittent fasting, you have to learn to differentiate this from true hunger.

My advice: Start decreasing overall sugar in your diet two to three weeks before you start incorporating intermittent fasting into your routine. This will help stabilize glucose fluctuations, so you don't feel those intense cravings.

When should you break your fast?

OK, but how do you determine when to push through and when to just eat? If you are just starting out with intermittent fasting, I suggest assessing your hunger and energy levels regularly and keeping a journal of the patterns you notice. Here are some things to look out for:

Start slowly. Try out shorter fasting periods first to gauge whether you can handle intermittent fasting regularly. Over the course of two weeks, try 12- to 16-hour fasts every three days. After about two weeks, I notice most people getting results and feeling more energy. But, of course, this varies.

Track your moods. Happy, unhappy, anxious, cranky? Take note of these mood changes as you begin the process of intermittent fasting. If you notice your moods fluctuating, stop fasting for a couple of days and wait at least three to five days before trying again. Seek professional help if your moods do not stabilize once you stop fasting.

Monitor your sleep. Is it disturbed, or are you sleeping better? Fasting should help support your circadian rhythm, not throw it out of whack. If fasting is leaving you feeling tired and sluggish, take a few days off.

Be patient. It will take about two weeks for many of the benefits of intermittent fasting, such as increased energy and elevated mood, to take effect. Long-term effects in your blood work and health parameters will take longer, typically three months from my experience.

Be safe. If you feel dizzy, uncomfortable, or experience any other concerning symptoms, stop fasting completely and consult with a physician.

Still not sure if you should eat or trudge on? Before you decide to give in to hunger pangs try this: Drink water or tea. Make sure your selection has very little sugar and contains under 40 calories. Now, wait 30 minutes and see if your hunger subsides.

If you are still hungry, that is a sign that you should absolutely take a break from the fast. Making the choice to break a fast without feeling guilt is very important at the onset of this process. Your body is still adjusting, so be gentle with yourself. Break your fast with a healthy meal (think: veggies, protein, and healthy fats) and move on. If you decide to try again, consider shortening your fasting window.

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Is intermittent fasting safe for everyone?

Although fasting has been practiced for thousands of years and is generally considered safe, there are some people who should not try it. Do not intermittent fast if you are missing monthly periods, having exaggerated PMS symptoms, if you are pregnant or breastfeeding, or feeling any type of hormonal disturbance. You should also consult with a physician if you are on any medications that can be affected by fasting.

Getting started with intermittent fasting and gauging your progress can be very personal. There is not enough research yet to give us exact instructions. Be sure to talk with an expert or your personal physician to safely try fasting.